JP2000244051A - Semiconductor laser driving circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laser driving circuit allowed for integration and IC, as the driving circuit for a semiconductor laser of short wavelength blue violet that exceeds 2.0 eV of band gap value of a semiconductor material. SOLUTION: A drive current supply circuit 30 which supplies a drive current to a semiconductor laser floats a power source voltage according to the band gap value of a semiconductor material so that a voltage exceeding the band gap value of the semiconductor material is applied between both ends of the semiconductor laser. The drive current is supplied to the drive current supply circuit 30 while applied with offset by a voltage shift circuit 20 according to the band gap value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to, for example, GaN
The present invention relates to a circuit for driving a semiconductor laser having a band gap value of more than 2.0 eV, such as a blue-violet semiconductor laser made of a group III-V semiconductor material such as (gallium nitride).

[0002]

2. Description of the Related Art In a recording / reproducing apparatus for an optical disk medium, an optical output from a semiconductor laser light source mounted on an optical pickup device is condensed on an optical disk medium by an objective lens. The intensity of the light output of the laser light source is modulated based on the recording signal,
Irradiation on the optical disk medium forms a recording mark on the optical disk medium.

For example, when a signal is recorded on a phase change recording medium, the light output of a semiconductor laser as a light source is usually intensity-modulated, and for example, an emission pulse train LP as shown in FIG. The recording mark is formed by irradiating the recording light on the upper side and performing recording compensation.

FIG. 3 (F) records a 5T mark MK (see FIG. 3 (B)) modulated in synchronization with a clock CLK (see FIG. 3 (A)) by the (1, 7) modulation method. The light emission waveform in this case is illustrated, but in order to accurately form a mark on the phase change optical recording medium, the light emission output value is, as shown in FIG.
1, the bias level Bias, and the peak level Peak, and the number of irradiation pulses, the irradiation position of each pulse, and the irradiation width are individually controlled according to the 2T to 8T recording marks.

When a signal is recorded (written) on a recording medium, data DT1 and DT2 corresponding to each light emission value (each of the above-mentioned level values) are generated in order to generate the above three-valued irradiation output LP based on the recording signal. , DT3 (FIGS. 3 (C), (D),
(E) is output from a pulse signal generator (not shown).

The data DT1 is a logic signal which is at a high level ("1") when the laser is turned on during reproduction (reading) and recording, and is at a low level ("0") when the laser is turned off. This data DT
1 is recording compensation data corresponding to the cooling level Cool.

The data DT2 is recorded at the time of recording.
This is a logic signal that goes to a high level (“1”) when irradiation is performed at the bias level Bias and the peak level Peak. This data DT2 is recording compensation data corresponding to the bias level Bias.

[0008] Further, the data DT3 is recorded only when the irradiation at the peak level Peak is performed.
This is a logic signal that becomes high level (“1”). This data DT3 is recording compensation data corresponding to the peak level Peak.

FIG. 4 shows an example of a semiconductor laser drive circuit in an apparatus for recording and reproducing signals on a phase-change optical recording medium using an InGaAlP-based red semiconductor laser as a light source of an optical pickup.

The semiconductor laser drive circuit shown in FIG. 4 is normally operated by a single power supply of + 5V. In this example, three sets of recording data D corresponding to the three emission values are used.
A first PNP transistor pair 2, 3, which performs high-speed current switching corresponding to T1, DT2, DT3,
Three differential transistor pairs, that is, second PNP transistor pairs 5 and 6 and third PNP transistor pairs 8 and 9, are provided. In each of these three transistor pairs, the emitters of the pair of transistors are connected to each other to form a PECL (Positive Emitt).
er Coupled Logic).

A power supply terminal at which a common emitter connection point of the three transistor pairs passes through the current control transistors 1, 4, and 7 and a +5 V DC voltage through the resistors 11, 13, and 15, respectively. It is connected to the. The bases of the current control transistors 1, 4, 7
As will be described later, command voltages CTL1, CTL2, and CTL2 for strictly controlling the light emission output level of the semiconductor laser 10 are provided.
CTL3 is a light emission output value control circuit (Automati
c Power Control; supplied from APC circuit.

The collectors of one of the transistors 2, 5, 8 of the three transistor pairs are grounded through resistors 12, 14, 16, respectively. The collectors of the other transistors 3, 6 and 9 are connected to each other, and the common connection point is grounded through the semiconductor laser 10.

In the case of this example, the data DT1, DT2, DT3 of the three systems corresponding to the light emission values are PECL.
(Positive Emitter Coupled
A (Logic) level differential pair signal of (+, −) is supplied to one and the other of the transistor pair, respectively.

That is, the differential pair signals DT1 (+) and DT1 (-) of the recording compensation data corresponding to the cooling level Cool are input to the bases of the first PNP transistor pairs 2 and 3 which perform high-speed current switching. Is done. When the data DT1 is at a high level (corresponding to reproduction and recording), the transistor 2 is turned off and the transistor 3 is turned off, a current flows to the anode side of the semiconductor laser 10, and the data DT1 is at a low level. In the case of (corresponding to laser off), a current flows through the resistor 12.

Similarly, differential pair signals DT2 (+) and D of recording compensation data corresponding to bias level Bias
T2 (−) is input to each base of the second transistor pair 5, 6. When the data DT2 is at a high level (corresponding to the bias level Bias and the peak level Peak data at the time of recording), a current flows to the anode side of the semiconductor laser 10, and the data DT2
Is low level (corresponding to a light emission mode other than the above), a current flows through the resistor 14.

Further, differential pair signals DT3 (+) and DT3 of the recording compensation data corresponding to the peak level Peak.
(−) Is input to each base of the third transistor pair 8 and 9. When the data DT3 is at a high level (corresponding to the peak level Peak data at the time of recording), a current flows to the anode side of the semiconductor laser 10, and the data DT3 is at a low level (corresponding to other light emission modes). In this case, a current flows through the resistor 16.

In the above configuration, the switching currents of the three systems are added to the current and injected into the semiconductor laser 10. For example, at the peak level Peak, the semiconductor laser 1
When 0 is emitted, all three switching currents are injected into the semiconductor laser 10.

In order to strictly control the respective light emission output levels, instruction voltages CTL1, CTL2, and CTL3 from an APC circuit (not shown) are applied to the current control transistors 1, 4, and 7 of the above-described three current switching circuits.
Is input to each base.

In the APC circuit, the semiconductor laser 10
Is constantly monitored, and in each mode such as recording / reproduction, the light output of the semiconductor laser 10 is controlled so as to always match the value specified by the CPU or the like. That is, the APC circuit plays a role of correcting the current-light emission output characteristic of the semiconductor laser 10 that changes depending on the operating environment temperature or the like.

[0020]

By the way, in the optical disk recording / reproducing apparatus, high recording density is demanded. In order to increase the recording density, it is necessary to reduce the spot size d on the optical disk medium.

The spot size d on the optical disk medium is given by d = λ / NA (Equation 1). The shorter the wavelength λ of the light source, the larger the numerical aperture NA of the objective lens. ,
The value becomes small, and high-density recording becomes possible.

As a method for shortening the wavelength λ of the light source, a GaN semiconductor laser developed by Nakamura et al. Is known (reference: Shuji Nakamura, et al., "Continuo").
us-wave operation of InGaN / GaN / AlGaN-based laser d
iodes grown on GaN substrate, "Appl. Phys. Lett. 7
2, 2014-2016 (1998)., Etc.). This is the emission wavelength λ
Are blue-violet light emitting elements of about 400 nm.

Here, the energy Ep of a photon corresponding to a wavelength of 400 nm is Ep = h · ω (Equation 2) (h is Planck's constant, ω represents 2πc / λ, and c is the speed of light.) When a semiconductor laser emits light, it is generally necessary to apply a voltage higher than a value obtained by dividing this energy by the electric charge e between the anode and cathode terminals of the semiconductor laser. That is, in the above example, an applied voltage of 3.1 V or more is required. Also, III-
The band gap energy of the GaN material belonging to Group V is about 3.6 eV, and it is expected that an applied voltage of 5 V or more is required in consideration of a voltage drop in an electrode or the like during current injection.

As shown in FIG. 5, FIG. 2 shows a typical current-output characteristic and a current-voltage characteristic of the same semiconductor laser, and a terminal voltage at an emission output of 20 mW is about 7
V, and the current at that time is an actual measurement value of about 200 mA.

For example, in the above-described InGaAlP-based red semiconductor laser, the voltage drop between the anode and the cathode of the semiconductor laser during operation is about 2.5 V, and a single 5 V power supply as shown in FIG. An operating driver circuit can be formed, and an IC can be formed.

On the other hand, in a GaN-based blue-violet semiconductor laser, as shown in FIG. 5, a voltage drop of 5 V or more occurs between the anode and the cathode. It is impossible to configure a laser drive circuit with a power supply, and it is very difficult to make an IC.

The InG described in the above-mentioned reference is used.
When an aN / GaN / AlGaN semiconductor laser is used as a light source of a recording / reproducing apparatus for a phase change optical recording medium, for example,
It is conceivable to configure a semiconductor laser drive circuit with a single 10V power supply.

However, as shown in the reference, 20 peaks corresponding to the recording peak level Peak.
At the mW output, a current of 200 mA is required, so that the power consumption of the laser driving circuit is large, and
Since high withstand voltage characteristics are required for IC integration, integration may be difficult.

In order to increase the operating speed of the LSI, it is usual to increase the speed by reducing the internal pattern and reducing the voltage. However, as described above, a single power supply of 10 V is used. In the case of using, there is a problem that it is difficult to increase the speed.

A blue-violet semiconductor laser is promising as a short-wavelength light source for next-generation optical disk devices. However, when the power consumption of the laser drive circuit is large and integration and IC integration are difficult, it is necessary to use a portable laser device. It hinders application.

The present invention has been made in view of the above problems, and has been described as an integrated circuit for driving a short-wavelength blue-violet semiconductor laser.
It is an object of the present invention to provide a semiconductor laser drive circuit that can be integrated into an IC.

[0032]

In order to solve the above problems, a semiconductor laser driving circuit according to the present invention is a semiconductor laser driving circuit which emits or modulates a short-wavelength semiconductor laser having a band gap value of a semiconductor material exceeding 2.0 eV. A circuit for supplying a drive current to the semiconductor laser, wherein a power supply voltage is floated in accordance with a band gap value of the semiconductor material, and the semiconductor laser is disposed between both ends of the semiconductor laser. A drive current supply circuit configured to apply a voltage exceeding a band gap value of a material, and a voltage shift circuit configured to supply the drive current having an offset corresponding to the band gap value to the drive current supply circuit. And characterized by the following.

In the semiconductor laser drive circuit according to the present invention having the above-described configuration, the drive current supply circuit includes:
The power supply voltage is not a single power supply, but is floated, and a voltage E exceeding the band gap value is applied between the anode and the cathode of the semiconductor laser. Then, the drive current is offset by a voltage corresponding to the voltage E and supplied to the semiconductor laser, whereby the semiconductor laser is driven.

According to the configuration of the present invention, a voltage of, for example, 5 V can be supplied to the drive current supply circuit as the floating power supply voltage. Therefore, even a driving circuit for a short-wavelength blue-violet semiconductor laser can be integrated and integrated.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a semiconductor laser drive circuit according to the present invention will be described below with reference to FIG. FIG. 1 shows that the above-mentioned InGaN /
This is an example of a semiconductor laser drive circuit for an optical disk recording / reproducing device using a blue-violet semiconductor laser using GaN / AlGaN as a light source.

As shown in FIG. 1, the semiconductor laser drive circuit of this embodiment is roughly composed of two circuit blocks, a voltage shift circuit 20 and a current switching circuit 30. These two circuit blocks 20 and 3
Each of the 0s can be made into an IC.

The circuit block of the voltage shift circuit 20 includes the above-mentioned three systems of light emission data DT1, DT2, DT3 output from a pulse signal generator (not shown).
Is a circuit for shifting the voltage. This voltage shift circuit 2
0 denotes three voltage shift circuit units 2 for shifting respective voltages of the three systems of light emission data DT1, DT2, DT3.
1, 22, and 23.

The three voltage shift circuit units 21, 22,
23 has exactly the same configuration. FIG. 2 illustrates a configuration example of the voltage shift circuit unit. FIG. 2 shows the case of the voltage shift circuit section 21 to which the light emission data DT1 is supplied.

As in the case of the red semiconductor laser shown in FIG. 4, the recording data of the three systems is input as a differential pair signal of the PECL level, and its voltage is about when the data is at the high level. When the data is at a low level, the voltage is about 3.1 V.

In the voltage shift circuit section 21, the NPN transistor pairs 51 and 52 have their emitters connected to each other, and their emitter common connection point is connected to the constant current circuit 60. The collector of each of the transistor pairs 51 and 52 has a voltage dividing resistor 53 connected between a first power supply terminal from which a DC voltage of +5 V is obtained and a second power supply terminal from which a DC voltage of +10 V is obtained. , 54 and the connection midpoint of the voltage dividing resistors 55 and 56, respectively.

The constant current circuit 60 includes an NPN transistor 6
1, resistors 62, 63, 64, and a diode 65. The transistor 61 has an emitter resistor 6
2. The operating current of the voltage shift differential circuit is controlled together with the base voltage circuit (consisting of the resistors 63 and 64 and the diode 65). In this example, the current is set to 5 mA.

In this example, resistance 53 = resistance 55 = 160Ω resistance 54 = resistance 56 = 270Ω, and the collector voltage of the off-side transistors of the NPN transistor pairs 51 and 52 becomes about 8.9V. It is set as follows. As described above, the on-side transistors of the NPN transistor pairs 51 and 52 have 5 mA.
, The collector output of the on-side transistor drops by 0.8 V to about 8.1 V.

As shown in FIG. 2, the cooling level Co
ol, a differential pair signal DT1 of the recording compensation data corresponding to
(+) And DT1 (-) are input to the bases of the NPN transistor pairs 51 and 52. Then, by taking out the collector outputs of the transistors 51 and 52, the voltage-shifted circuit unit 21 can obtain the voltage-shifted differential pair signals DT1s (+) and DT1s (-).

In other words, the input PECL differential signals DT1 (+) and DT1
By shifting the level of (−) by 5 V, it becomes possible to make the data high level about 8.9 V and the data low level about 8.1 V.

Similarly, in the voltage shift circuit section 22,
The differential pair signals DT2 (+) and (−) of the recording compensation data corresponding to the bias level Bias are shifted by 5V, and the voltage-shifted differential pair signals DT2s are shifted.
(+) And DT2s (-) are obtained. Further, in the voltage shift circuit 23, the differential pair signals DT3 (+) and DT3 of the recording compensation data corresponding to the peak level Peak.
3 (-) is shifted by 5V, and the voltage-shifted differential pair signals DT2s (+) and DT2s (-) are shifted.
Is obtained.

In this manner, the voltage shift circuit 20 outputs three differential pair signals DT1s (+), DT1s (-), and DT2s which are voltage-shifted to about 8.9V at high level and about 8.1V at low level. (+) And DT2s
(−), DT3 (+) and DT3 (−) are obtained and supplied to the current switching circuit 30, respectively.

The current switching circuit 30 is a circuit for injecting a current into the GaN semiconductor laser by using the differential pair signal voltage-shifted by the voltage shift circuit 20,
The operating principle is the same as that of InGaAl described above with reference to FIG.
This is almost the same as the laser drive circuit in the P-based red semiconductor laser.

However, the current switching circuit 3 of this example
4 is different from the laser drive circuit of FIG. 4 in that a single power supply of 5 V is further shifted by 5 V to operate between a first power supply voltage of +5 V and a second power supply voltage of +10 V. ing.

That is, the three differential transistor pairs of the first PNP transistor pair 32, 33, the second PNP transistor pair 35, 36, and the third PNP transistor pair 38, 39, which perform high-speed current switching, are provided. Provided. In each of these three transistor pairs, the emitters of the paired transistors are connected together to form a PECL (Positive Emitt).
er CoupledLogic).

The emitter common connection points of the three transistor pairs are connected to the current control transistors 31, 34, 3
7 are connected to a second power supply terminal through which a DC voltage of +10 V is obtained through the resistors 41, 43, and 45, respectively. Current control transistors 31, 3
A short wavelength blue-violet semiconductor laser 40 is
Command voltage CT for strictly controlling the light emission output level of
L1, CTL2, and CTL3 are supplied from a light emission output value control circuit (Automatic Power Control; APC circuit) not shown.

The collectors of the transistors 32, 35, 38 of each of the three transistor pairs are:
Each is connected to a + 5V first power supply terminal through resistors 42, 44, 46, and the other transistors 43, 46,
The collectors 49 are connected to each other, and the common connection point is grounded through the semiconductor laser 40.

The three systems of recording compensation data supplied to the current switching circuit 30 are output from the voltage shift circuit 20 in the form of voltage-shifted three-system differential pair signal outputs DT1s (+) and DT1s (-). ), DT2s
(+) And DT2s (-), DT3 (+) and DT
3 (-).

Then, the voltage shift differential pair signal DT1s of the recording compensation data corresponding to the cooling level Cool
(+) And DT1s (-) are input to the bases of the first PNP transistor pairs 32 and 33 that perform high-speed current switching. Then, the voltage shift data DT
When 1 s is at a high level (corresponding to reproduction and recording), the transistor 32 is turned off and the transistor 33 is turned off, a current flows to the anode side of the semiconductor laser 40, and the voltage shift data DT 1 s is at a low level ( In the case of “laser off”, a current flows through the resistor 42.

Similarly, the voltage shift differential pair signal DT2s of the recording compensation data corresponding to the bias level Bias
(+) And DT2s (-) are input to each base of the second transistor pair 35 and 36. When the voltage shift data DT2s is at a high level (corresponding to the bias level Bias and the peak level Peak data at the time of recording), a current flows to the anode side of the semiconductor laser 40, and the voltage shift data DT2s is at a low level ( In the case of a light emission mode other than the above, a current flows through the resistor 44.

The voltage-shift differential pair signals DT3 (+) and DT3 (-) of the recording compensation data corresponding to the peak level Peak are supplied to the third transistor pair 38,3.
9 is input to each base. Then, the voltage shift data DT3s is at a high level (the peak level P at the time of recording).
eak data), a current flows on the anode side of the semiconductor laser 40, and the voltage shift data DT
When 3s is at a low level (corresponding to a light emission mode other than the above), a current flows through the resistor 46.

In the above configuration, the switching currents of the three systems are added to the current and injected into the semiconductor laser 40. For example, at the peak level Peak, the semiconductor laser 4
When emitting 0, all three switching currents are injected into the semiconductor laser 40.

As described above, the three switching currents are added to the current and injected into the semiconductor laser.
The respective light emission output levels correspond to the current control transistors 3 of the three current switching circuits, similarly to the laser drive circuit in the InGaAlP red semiconductor laser.
1, 34 and 37.

In the GaN semiconductor laser described in the reference described in the section of the conventional example, a voltage drop of about 7 V occurs between the anode and the cathode. As described above, the drive circuit of the above-described embodiment is used. Thus, the operating potential of the transistor pair that performs current switching can be set to 8 V or more, so that the light emission output of the GaN semiconductor laser having a large terminal voltage can be modulated.

Further, by operating the current switching circuit 30 with an offset of 5 V, the power consumption of the semiconductor laser driving circuit is kept substantially the same as that of the conventional driving circuit of the InGaAlP-based red semiconductor laser, and the integration of the circuit is improved. Can be possible.

[Modification] In the above embodiment,
Although the GaN semiconductor laser is configured as a semiconductor laser drive circuit with the polarity of the cathode common (the cathode terminal is connected to the case and operates by injecting current from the anode terminal), the element having the anode common polarity is also used. The drive circuit can be configured in exactly the same manner. In that case, the anode terminal is connected to the case, and the drive current is drawn in the negative direction from the cathode terminal. Therefore, the current switching circuit is offset by, for example, -5V, and operates between "-5V" and "-10V". Let it.

It is preferable that the operation offset voltage applied to the semiconductor laser drive circuit is set to a voltage between the anode and the cathode terminals during the laser operation, but it is also possible to set the voltage to a lower voltage and operate the laser. It is.

Further, the semiconductor laser driving circuit is not operated at 5 V shown in the above embodiment, but is operated at 3.3 V, for example.
It can be designed as a V operation circuit. That is,
In the above example, the semiconductor laser driving circuit is
What is necessary is just to operate between 6.7V.

Further, in the above description of the embodiment, the drive circuit is constituted by using the high-speed current switching circuit formed by the transistor pair. However, the drive circuit is constituted by using another semiconductor element such as GaAs FET and integrated. Is also possible.

[0064]

As described above, according to the semiconductor laser driving circuit of the present invention, a blue-violet semiconductor laser having a substantially large voltage drop between the anode and the cathode is applied as a light source of an optical recording medium recording / reproducing apparatus. It is possible to

Further, by applying a voltage offset exceeding the band gap of the semiconductor material to the drive circuit and operating it, the power consumption in the laser drive circuit can be reduced by the conventional InGaA.
It can be suppressed to almost the same level as a drive circuit using an AlP-based red semiconductor laser.

By applying the present invention, G
A drive circuit for an aN semiconductor laser can be integrated (integrated into an IC), and a blue-violet semiconductor laser, which is expected as a light source for a next-generation optical disk device, has been put into practical use. Can be made possible.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment of a semiconductor laser drive circuit according to the present invention.

FIG. 2 is a circuit diagram showing a configuration example of a voltage shift circuit unit which is a part of FIG.

FIG. 3 is a diagram for explaining data supplied to a semiconductor laser drive circuit.

FIG. 4 is a circuit diagram of an example of a conventional semiconductor laser drive circuit.

FIG. 5 is a diagram for explaining characteristics of a blue-violet short wavelength semiconductor laser.

[Explanation of symbols]

Reference Signs List 20: voltage shift circuit, 21, 22, 23: voltage shift circuit section, 30: current switching circuit, 40: short wavelength semiconductor laser, 31, 34, 37: current control transistor, 32, 33: transistor pair, 35, 36 ... Transistor pairs, 38, 39 ... Transistor pairs, 41-
46: resistor, 51, 52: transistor pair, 53, 5
4: voltage dividing resistor, 55, 56: voltage dividing resistor, 60: constant current circuit

Claims (10)

[Claims] The semiconductor material has a band gap value of 2.0.
A semiconductor laser driving circuit that emits or modulates a short wavelength semiconductor laser exceeding eV, wherein a power supply voltage is floated according to a band gap value of the semiconductor material, and a signal for driving the semiconductor laser includes the band. An offset according to a gap value is provided to the semiconductor laser drive circuit. 2. The method according to claim 1, wherein the short-wavelength semiconductor laser is made of GaN or the like.
2. The semiconductor laser drive circuit according to claim 1, wherein the semiconductor laser drive circuit is a blue-violet semiconductor laser made of a group III-V semiconductor material. 3. A semiconductor material having a band gap value of 2.0.
A semiconductor laser driving circuit that emits or modulates a short-wavelength semiconductor laser exceeding eV, wherein the circuit supplies a driving current to the semiconductor laser, and a power supply voltage is floated according to a band gap value of the semiconductor material. A driving current supply circuit configured to apply a voltage higher than a band gap value of the semiconductor material between both ends of the semiconductor laser; and a driving current supplied with an offset corresponding to the band gap value. And a voltage shift circuit for supplying the driving current to the driving current supply circuit. 4. The driving current is a switching current, the driving current supply circuit is configured as a current switching circuit, and the driving current supply circuit and the voltage shift circuit include a differential pair of transistors. 4. The semiconductor laser driving circuit according to claim 3, wherein the driving circuit is configured. 5. The semiconductor laser drive circuit according to claim 4, wherein said drive current supply circuit and said voltage shift circuit are formed as ICs. 6. The short-wavelength semiconductor laser, such as GaN.
6. The semiconductor laser drive circuit according to claim 4, wherein the semiconductor laser drive circuit is a blue-violet semiconductor laser made of a III-V group semiconductor material. 7. The semiconductor material has a band gap value of 2.0 e.
A current switching circuit that drives a short-wavelength semiconductor laser exceeding V, emits or modulates the current by driving the switching current, and a voltage shift circuit that shifts the voltage of the switching current supplied to the current switching circuit. A short wavelength semiconductor laser having a bandgap value of a semiconductor material exceeding 2.0 eV is connected between one collector of a pair of transistors whose emitters are coupled to each other and a ground terminal, and the other collector of the transistor of the pair of transistors is connected. Is connected to a first power supply terminal to which a first DC voltage is applied via a first resistor, and a common connection point of the emitters of the pair of transistors is connected via at least a second resistor. A first power supply connected to a second power supply terminal that obtains a second DC voltage higher than the first DC voltage; The voltage and the second power supply voltage are selected such that a voltage corresponding to or higher than the band gap value is applied to the semiconductor laser. The voltage shift is applied to the bases of the pair of transistors. A differential pair signal for switchingly driving the semiconductor laser is supplied from a circuit, wherein the voltage shift circuit comprises a transistor having a common connection point of the emitters of a pair of transistors whose emitters are coupled to each other. A differential pair signal for driving the semiconductor laser is supplied to a base of the pair of transistors, and a collector of each of the pair of transistors is a first power supply of the first DC voltage. Connected to a connection midpoint of a voltage dividing resistor connected between a terminal and a second power supply voltage of the second DC voltage; A semiconductor laser drive circuit, wherein a voltage-shifted differential pair signal obtained at a point is supplied to a base of a pair of transistors of the current switching circuit. 8. The semiconductor laser driving circuit according to claim 7, wherein the data for driving the semiconductor laser is a plurality of data, and the current switching circuit includes the pair of transistors,
The circuit configuration having first and second resistors is provided only for the plurality of data, and the collectors of one of the plurality of pairs of transistors are commonly connected to each other, and the common connection point and the ground are connected. A short wavelength semiconductor laser having a band gap value of a semiconductor material exceeding 2.0 eV is connected between the plurality of data shift circuits, and the voltage shift circuit includes a plurality of voltage shift circuits provided for each of the plurality of data. With a circuit part,
The semiconductor laser drive circuit, wherein each data is supplied as each of the differential pair signals to each of the voltage shift circuit units. 9. The semiconductor laser drive circuit according to claim 7, wherein said current switching circuit and said voltage shift circuit are each formed as an IC. 10. The semiconductor laser according to claim 5, wherein said semiconductor laser is a III-
10. The semiconductor laser drive circuit according to claim 7, wherein the semiconductor laser drive circuit is a blue-violet semiconductor laser made of a group V semiconductor material.